fix(gateway): preserve paced qualification traffic

gateway/qualification_process_test.go

@@ -76,6 +76,11 @@ type qualificationProcessRecordResult struct {
 	RecordingElapsed time.Duration
 }
 
+type qualificationProcessTimingSample struct {
+	elapsed     time.Duration
+	observation mediaTimingObservation
+}
+
 type qualificationProcessRecorder struct {
 	mu            sync.Mutex
 	active        bool
@@ -89,6 +94,8 @@ type qualificationProcessRecorder struct {
 	recordErr     error
 	tickerStop    chan struct{}
 	tickerDone    chan struct{}
+	timingSamples chan qualificationProcessTimingSample
+	timingDone    chan struct{}
 	clock         time.Duration
 }
 
@@ -135,6 +142,9 @@ func (r *qualificationProcessRecorder) start(request qualificationProcessRecordR
 	r.clock = clock
 	r.tickerStop = make(chan struct{})
 	r.tickerDone = make(chan struct{})
+	r.timingSamples = make(chan qualificationProcessTimingSample, 4096)
+	r.timingDone = make(chan struct{})
+	go r.writeTimings()
 	go r.sampleResources()
 	return nil
 }
@@ -142,13 +152,24 @@ func (r *qualificationProcessRecorder) start(request qualificationProcessRecordR
 func (r *qualificationProcessRecorder) observe(observation mediaTimingObservation) {
 	r.mu.Lock()
 	defer r.mu.Unlock()
-	if !r.active || r.recordErr != nil {
+	if !r.active {
 		return
 	}
-	_, r.recordErr = fmt.Fprintf(r.rawBuffered, "%d,%d,%d,%d\n",
-		time.Since(r.started).Nanoseconds(), observation.QueueDelay.Nanoseconds(),
-		observation.ProcessingDelay.Nanoseconds(), observation.PacingDelay.Nanoseconds())
-	r.samples++
+	r.timingSamples <- qualificationProcessTimingSample{
+		elapsed: time.Since(r.started), observation: observation,
+	}
+}
+
+func (r *qualificationProcessRecorder) writeTimings() {
+	defer close(r.timingDone)
+	for sample := range r.timingSamples {
+		if r.recordErr == nil {
+			_, r.recordErr = fmt.Fprintf(r.rawBuffered, "%d,%d,%d,%d\n",
+				sample.elapsed.Nanoseconds(), sample.observation.QueueDelay.Nanoseconds(),
+				sample.observation.ProcessingDelay.Nanoseconds(), sample.observation.PacingDelay.Nanoseconds())
+		}
+		r.samples++
+	}
 }
 
 func (r *qualificationProcessRecorder) sampleResources() {
@@ -177,9 +198,12 @@ func (r *qualificationProcessRecorder) stop() (qualificationProcessRecordResult,
 	}
 	r.active = false
 	stop, done := r.tickerStop, r.tickerDone
+	timings, timingDone := r.timingSamples, r.timingDone
+	close(timings)
 	r.mu.Unlock()
 	close(stop)
 	<-done
+	<-timingDone
 
 	r.mu.Lock()
 	r.resources = append(r.resources, qualificationRuntimeSample(r.started))